Lesson Overview Cell Structure
Cell Organization
– The eukaryotic cell
can be divided into
two major parts: the
nucleus and the
cytoplasm.
– The cytoplasm is
the fluid portion of
the cell outside the
nucleus.
– Prokaryotes do not
have a nucleus
Lesson Overview Cell Structure
Cell Organization
– Organelles “little
organs.”
– Example:
mitochondria, golgi
apparatus,
endoplasmic reticulum
Lesson Overview Cell Structure
The Nucleus
– the nucleus is the control center of the cell.
– It contains nearly all the cell’s DNA.
Lesson Overview Cell Structure
The Nucleus
– The nucleus is
surrounded by a
nuclear envelope
composed of two
membranes.
Lesson Overview Cell Structure
The Nucleus
– The nuclear
envelope is dotted
with thousands of
nuclear pores,
which allow
material to move
into and out of the
nucleus.
Lesson Overview Cell Structure
The Nucleus
– Proteins and RNA,
move through the
nuclear pores to and
from the rest of the
cell.
Lesson Overview Cell Structure
The Nucleus
– Chromosomes
contain the genetic
information that is
passed from one
generation of cells to
the next.
– They are found in
the nucleus.
– chromatin—DNA
bound to proteins.
Lesson Overview Cell Structure
The Nucleus
– a small, dense region in the
nucleus is called the
nucleolus.
– The nucleolus is where the
assembly of ribosomes
begins.
Lesson Overview Cell Structure
Vacuoles
– Vacuoles large, saclike, membrane-
enclosed structures
– They store water, salts, proteins, and
carbohydrates.
Lesson Overview Cell Structure
Vacuoles
In plant cells the pressure of the vacuole increases their
rigidity, making it possible for plants to support heavy
structures such as leaves and flowers.
Lesson Overview Cell Structure
Vacuoles
– The paramecium
contains an organelle
called a contractile
vacuole which pumps
excess water out of
the cell.
Lesson Overview Cell Structure
Vesicles
– Vesicles are used to store and move materials between
cell organelles, as well as to and from the cell surface.
Lesson Overview Cell Structure
Lysosomes
– Lysosomes are small organelles filled with enzymes that
function as the cell’s cleanup crew.
– Lysosomes remove “junk” that might accumulate and
clutter up the cell.
istockphoto.com
Lesson Overview Cell Structure
Lysosomes
– breakdown of lipids, carbohydrates, and proteins into
small molecules that can be used by the rest of the cell.
Lesson Overview Cell Structure
Lysosomes
– Break down organelles that have outlived their
usefulness.
Helps break down endometrial
lining of the uterus to cause
menstrual flow
Helps digest tissue to form
fingers in the fetus
Lesson Overview Cell Structure
The Cytoskeleton
– Gives eukaryotic
cells their shape
and internal
organization.
– Microfilaments
and microtubules
are two of the
principal protein
filaments that make
up the
cytoskeleton.
Lesson Overview Cell Structure
Microfilaments
– Threadlike
structures made up
of a protein called
actin.
– Helps support the
cell.
– Help cells move.
Lesson Overview Cell Structure
Microtubules
– Hollow structures
made up of proteins
known as tubulins.
– Maintain cell shape.
– Important in cell
division.
Lesson Overview Cell Structure
Ribosomes
– small particles of RNA and protein found in the
cytoplasm; they produce proteins.
– The instructions to make proteins come from DNA.
Lesson Overview Cell Structure
Endoplasmic Reticulum
– internal membrane system of
the cell is known as the
endoplasmic reticulum, or
ER.
– This is where lipid components
of the cell membrane are
assembled, along with
proteins and other materials
that are exported from the cell.
– The ER is divided into smooth
ER & rough ER.
Lesson Overview Cell Structure
Rough Endoplasmic Reticulum or Rough
ER
– involved in the
synthesis &
modification of
proteins
– It is called rough
because of the
ribosomes found on
its surface.
Lesson Overview Cell Structure
Smooth Endoplasmic Reticulum or
Smooth ER
– Is called smooth ER
because ribosomes
are not found on its
surface.
– It contains enzymes
that make
membrane lipids and
the detoxify drugs.
Lesson Overview Cell Structure
Golgi Apparatus
– Proteins produced in the rough ER move to the Golgi
apparatus
– It appears as a stack of flattened membranes.
Lesson Overview Cell Structure
– It modifies, sorts, and packages proteins and
other materials from the ER for storage in the cell
or release outside the cell.
Golgi Apparatus
Lesson Overview Cell Structure
– From the Golgi apparatus, proteins are
“shipped” to their final destination inside or
outside the cell.
Golgi Apparatus
Lesson Overview Cell Structure
Organelles That Capture and Release
Energy
– The primary source of energy for plants is the SUN
– Your body cells get energy from food (plants and
animals).
– Chloroplasts and mitochondria are both involved in
energy conversion processes within the cell.
Lesson Overview Cell Structure
Chloroplasts
Plants and some other
organisms contain
chloroplasts.
Chloroplasts capture
energy from sunlight
and convert it into
food that contains
chemical energy.
CHLOROPLASTS are the biological equivalents
of solar power plants
Lesson Overview Cell Structure
Photosynthesis
Photosynthesis
process where plants
make carbohydrates
and oxygen using
sunlight energy,
carbon dioxide, and water.
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Lesson Overview Cell Structure
Chloroplasts
– Two membranes surround chloroplasts.
– Inside the organelle are large stacks of other
membranes, which contain the green pigment
chlorophyll.
Lesson Overview Cell Structure
Mitochondria
– Nearly all eukaryotic cells, including plants, contain
mitochondria.
– Mitochondria are the power plants of the cell.
– They convert the chemical energy stored in food into
compounds that are more convenient for the cell to use.
Lesson Overview Cell Structure
Mitochondria
– Two membranes— an outer membrane and an inner
membrane —enclose mitochondria. The inner
membrane is folded up inside the organelle.
Lesson Overview Cell Structure
Mitochondria
– In humans, all or
nearly all of our
mitochondria come
from the cytoplasm of
the ovum, or egg cell.
You get your
mitochondria from
Mom!
Lesson Overview Cell Structure
Mitochondria
– Chloroplasts and
mitochondria contain
their own genetic
information in the form
of small DNA
molecules.
– The endosymbiotic
theory suggests that
chloroplasts and
mitochondria may
have descended from
independent
microorganisms.
Lesson Overview Cell Structure
Cellular Boundaries
– The barrier surrounding the cell is the cell membrane
– It (1) regulates what enters and leaves the cell and also (2) protects and (3) supports the cell.
Lesson Overview Cell Structure
Cellular Boundaries
– Plant cells and most
prokaryotes have a strong
supporting layer around
the membrane known as
a cell wall.
– The main function of the
cell wall is to provide
support and protection for
the cell.
Lesson Overview Cell Structure
Cell Walls
– Many prokaryotes,
plants, algae, and
fungi, have cell walls.
Animal cells do not
have cell walls.
– Cell walls lie outside
the cell membrane and
most are porous
enough to allow water,
oxygen, carbon
dioxide, and certain
other substances to
pass through easily.
Lesson Overview Cell Structure
Lipid bilayer
– It is a double-layered sheet found in nearly all cell
membranes.
– It gives cell membranes a flexible structure and forms
a strong barrier between the cell and its surroundings
Lesson Overview Cell Structure
Lipid bilayer
– Composed of
phospholipids
– The fatty acid portions
of such a lipid are
hydrophobic, or
“water-hating,” while
the opposite end of the
molecule is
hydrophilic, or “water-
loving.”
Lesson Overview Cell Structure
The Fluid Mosaic Model
– Most cell membranes contain protein molecules that
are embedded in the lipid bilayer.
– Carbohydrate molecules are attached to many of
these proteins.
Lesson Overview Cell Structure
The Fluid Mosaic Model
– Fluid- because the
proteins in the lipid
bilayer can move
around and “float”
among the lipids.
– Mosaic- because so
many different kinds of
molecules make up
the cell membrane
MOSAIC
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The Fluid Mosaic Model of the cell membrane
Lesson Overview Cell Structure
The Fluid Mosaic Model
– Some of the proteins form channels and pumps that
help to move material across the cell membrane.
– Many of the carbohydrate molecules act like chemical
identification cards, allowing individual cells to identify
one another.
Lesson Overview Cell Structure
The Fluid Mosaic Model
– If a substance is unable
to cross a membrane, the
membrane is said to be
impermeable to it.
– If a substance is able to
cross a membrane, the
membrane is said to be
permeable to it.
Although many substances can cross
biological membranes, some are too large
or too strongly charged to cross the lipid
bilayer.